1. Field of the Invention
The present invention relates to a developing apparatus to be mounted in an image forming apparatus, which uses a recording technique such as an electrophotographic process, an electrostatic recording process or the like, like a copying machine, a printer and the like. In particular, the present invention relates to a developing apparatus suitable for being mounted in a process cartridge capable of being detachably attachable to an image forming apparatus.
2. Related Art
An image forming apparatus using an electrophotography requires maintenance, such as the exchange of its photosensitive body drum, the replenishment or the exchange of its developer, the adjustment, the cleaning or the exchange of its other parts (its charger, its cleaner container, or the like), when the image forming apparatus has been used for a long time. It is practically difficult for a person other than a serviceperson having an expert knowledge to do such maintenance work.
Accordingly, an image forming apparatus employing an electrophotographic image forming process has employed a process cartridge system in which an electrophotographic photosensitive body and process means working on the electrophotographic photosensitive body are integrally formed to be a cartridge and the cartridge is made to be detachably attachable to the main body of the image forming apparatus. Because the process cartridge system enables a user to perform the maintenance of the apparatus by himself or herself without relying on a serviceperson, the process cartridge system has been able to improve the operability of the image forming apparatus remarkably. Consequently, the process cartridge system is widely used in the image forming apparatus.
Thereby, when the maintenance of an aforesaid process device becomes necessary, a user himself or herself can simply maintain or exchange a process cartridge, and consequently, it has become able to obtain a high grade image quality cheaply and easily.
Developing means (or a developing apparatus) built in such a process cartridge is provided with seal members for preventing the outflow of toner to an area other than the developing area at both end portions of a developer bearing body such as a rotating developing roller mounted in the developing apparatus. An elastic body made of a felt, a expanded rubber or the like is widely used as a conventional seal member preventing the outflow of toner.
A developing roller is provided with a magnet roller therein, and is rotatably supported by a developing container with sleeve bearings. Consequently, toner fed from the developing container attaches to the surface of the developing roller by a magnetic force of the magnet roller. After the thickness of the attached toner layer has been regulated by a developing blade, the toner attaches to a latent image on a photosensitive drum at a position opposed to the latent image on the photosensitive drum as the developing roller rotates. Consequently, the latent image is developed.
The developing apparatus is further provided with elastic seal members attached at both end portions of the developing roller at the outsides of the developing area in the lengthwise direction thereof and at the inner part on the side opposite to the opening side of the developing roller attached to a developing frame body of the developing apparatus. The elastic seal member is pressed to the outer peripheral surface of the developing roller for preventing the outflow of toner.
As for the aforesaid contact type seal members, because the elastic seals are pressed to the half of the outer peripheral surface of the developing roller, the conventional developing apparatus has the problem such that the load of the developing roller, which rotates at the time of a developing operation, is large, and the problem such that the elastic seal members deteriorate owing to the contact with the developing roller to make the sealing performance of the elastic seal members worse. Moreover, toner sometimes enters into the gaps between the developing roller and the elastic seal members, although the amount of the so entering toner is small. The invasion of the toner sometimes causes an increase of torque or an increase of fluctuations of torque to produce the unevenness of the rotations of the developing roller. And then, a bad influence is sometimes exerted upon image formation.
Accordingly, for solving those problems, a noncontact type seal member has been proposed. In the noncontact type seal member, seal members made of a magnetic body (hereinafter referred to as xe2x80x9cmagnetic sealsxe2x80x9d) are disposed at both end portions of the developing roller with predetermined spaces between them for preventing the outflow of toner.
The magnetic seal is made of a magnet. The magnetic seals are attached to both end portions of the developing roller in the state of being wound around the end portions for being disposed with a predetermined gap (about 0.1 mm to 0.7 mm) to the outer peripheral surface of the developing roller. The magnetic seals are attached to the developing container in the wound state along with the developing roller. The surfaces of the magnetic seals opposed to the developing roller are magnetized. Magnetic brushes formed by chained toner formed along each line of magnetic force fill up the gaps between the outer peripheral surface of the developing roller and the surfaces of the magnetic seals to prevent the outflow of toner from the developing area.
Moreover, because it is needed to locate the magnetic seals highly precisely to the developing roller, various locating methods have conventionally been devised.
Incidentally, in both cases of the use of the aforesaid contact type seal member and the use of the noncontact type seal member, high accuracy of the attachment of them to the main body of the developing apparatus is required for securing their seal performances.
The present invention was made in consideration of the aforesaid problems, and an object of the invention is to provide a developing apparatus in which toner does not easily leak out.
Another object of the invention is to provide a developing apparatus in which seal members for preventing the leakage of the toner from the end portions of the developing roller can be attached with high accuracy.
A further object of the invention is to provide a developing member to which seal members for preventing the leakage of toner from the end portions of its developing roller can be attached simply and accurately.
A still further object of the invention is to provide a developing apparatus in which the positional accuracy of seal members to its developing roller is high.
A still further object of the invention is to provide a developing apparatus including a rotatable developer bearing member, a bearing member for holding the developer bearing member rotatably, and a seal member for preventing the leakage of a developer from an end portion of the developer bearing member in the lengthwise direction thereof into the lengthwise direction, wherein the seal member is located by the bearing member.
The still further object of the invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.